# Fast computer evaluation of radiative properties of hydrogenic systems

## Description

Abstract Three subroutines are described for the very fast calculation of bound-bound, bound-free, and free-free cross-sections for nonrelativistic hydrogenic systems of arbitrary nuclear charge and reduced mass. The first two are essentially exact, being based on recursion relations which are known to be stable. The third evaluates the thermally-averaged free-free Gaunt factor by means of a two-dimensional Chebyshev expansion calculated by numerical evaluation of the cross-sections expressed as hyper... Title of program: RADZ1 Catalogue Id: ABZS_v1_0 Nature of problem Although the cross sections for the absorption and emission of radiation by hydrogenic systems are known exactly in the nonrelativistic approximation, the analytic expressions are not easy to evaluate, especially for large values of the principal quantum number. However, for bound-bound and bound-free transitions, recursion techniques have proved to be accurate and stable for values of the principal quantum number as large as 500. For free-free transitions, recursion techniques are not applicabl ... Versions of this program held in the CPC repository in Mendeley Data ABZS_v1_0; RADZ1; 10.1016/0010-4655(91)90013-B This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2018)